1. Field of the Invention
The present invention relates to an image pickup unit that varies optical characteristics of an objective optical system used in an endoscope and the like and an endoscope provided with the image pickup unit.
2. Description of the Related Art
As is well known, endoscopes are widely used for observation, treatment, and the like of an inside of a body (an inside of a body cavity) of an organism or inspection, repairing, and the like of a plant facility for industrial use. In recent years, there is an endoscope in which an image pickup unit that can change a focal length is used for focus adjustment of a photographed image or a zooming function for performing magnification adjustment such as wide/tele. Note that a technique of the image pickup unit that can change the focal length in this way is used not only in the endoscope but also in various photographing devices.
For example, Japanese Patent Application Laid-Open Publication No. 2003-290134 discloses an image pickup unit provided in an endoscope apparatus. The conventional image pickup unit is configured to be capable of advancing and retracting a moving lens, which is a variable focus lens, along an optical axis to an always-focused focal position when an operation wire disposed in an insertion section is pushed and pulled from an operation section by a focus switching lever provided in the operation section.